Power control assistance device for motor vehicles

ABSTRACT

A power control assistance device provided with an actuator mechanically connected to the power control member to provide a directly controlled returned force to the power control member in direct opposition to the force exerted by the operator.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power control assistance device formotor vehicles having an internal combustion engine. It is particularlysuitable for controlling the speed and traction slippage of highwayvehicles, but this application of the invention is to be understood asone non-limitative example of its potential uses.

2. Discussion of Related Art

The comfort and power of highway motor vehicles as well as trafficconditions in today's world make compliance with speed limitsproblematical. The driver who wants to maintain his vehicle at themaximum speed authorized while not violating the regulations is forcedto pay great attention to his speedometer. A device capable ofeffectively assisting him in this task would be of great interest.

Prior devices for this purpose are known, among which three differentprinciples of operation can be distinguished:

cruise controls: they maintain the speed stable despite changes in thelayout of the road.

excess-speed alarms: they signal the exceeding of the maximum speed bymeans of a luminous or acoustic alarm.

speed limiters: they prevent exceeding the maximum speed, generally bypositioning a movable stop on the power control.

Apparatus based on these principles are little used, with the exceptionof cruise controls which the manufacturers offer as an option onhigh-class vehicles. French Patents 2 164 362, 2 537 742, 2 444 163, and2 632 578 may be mentioned as representative examples.

These devices present problems which it is the object of the inventionto solve, namely:

Cruise controls do not act as limiters and cannot be used in citytraffic; they do not permit natural slowing down by release of the pedaland they are put out of operation by actuation of the brake or clutch;

Alarms do not participate in automating the driving and they do notassist in maintaining the speed within a narrow range.

Limiters have the drawback of keeping the speed of the vehicle in check,or of placing a hard point on the stroke of the pedal which the controlmeans and the manner of action used make disagreeable for the driver andwhich is incompatible with the stabilizing of the speed.

SUMMARY OF THE INVENTION

The invention described below is the result of a different approach tothe problem and it combines the functions of these three devices withouthaving their limitations. It acts simultaneously, and by a singlesignaling, limiting and cruise-control means, and it can be used,whatever the traffic conditions are. It also leaves the driver a maximumfreedom of choice and does not change his driving habits, while veryeffectively assisting him.

The solution consists in producing a control loop in which the driver isintegrated as an active element. The device consists of at least a speedsensor, a set-speed selector, an electronic unit and an actuator. Thespeed of the vehicle is detected by a sensor and compared by theelectronic unit with the set speed which has been selected. When thespeed becomes greater than the speed set, the electronic unit controlsthe actuator, so as to produce a controlled return force on the powerregulating member that is directly under the control of the driver, forexample an accelerator pedal. This force, transmitted by a mechanicalconnection, is produced by a spring associated with a triangulationmechanism. A motor in the mechanism displaces the components of forceswhich act on the output member of the actuator. The return force on thepedal is thus regulated, without discontinuity, from a minimum value toa maximum value, regardless of its position, as a function of thecontrol signal which the actuator receives from the electronic unit.Thus, the invention does not deprive the driver of control of hisaccelerator:

The measurement of the excess speed is made known to him by a directperception which is related to his driving action; the return force onthe spring is directly related to the speed difference. It is no longernecessary to observe the speedometer.

The variations in intensity of this force are sufficient to assist thedriver in effortlessly and unconsciously correcting the position of theaccelerator pedal.

The foot of the driver is thus used both as speed sensor and asintelligent actor in the driving; the control of the speed is transposedto the instinctive control of a force and the driver can limit orstabilize the speed without any effort of attention. The technicalsolutions employed also enable the driver to override the action of thedevice at any time.

The limiting of traction slippage is based on the same principles, usingthe measured speed of the wheels. It can be noted that the invention isnot incompatible with other equipment (electronic injection, automatictransmissions, electronic gas valve, etc.) and that installing itrequires only a minor adaptation. It is, by its very nature, very safeand does not require any other maneuver on the part of the driver thanthe selection of the maximum speed. The simplicity of the means usedimplies a very low cost of manufacture and great reliability.

The detailed explanation of the operation given in the followingdescription makes it possible to note the scope and advantages of theseprinciples, as well as the technical solutions employed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a general block diagram;

FIG. 2 shows a variant of the connection;

FIG. 3 shows the principle of operation of the actuator;

FIG. 4 shows the principle of an embodiment integrated in the pedal;

FIG. 5 shows a variant with pedal;

FIG. 6 shows a variant embodiment of the actuator;

FIG. 7 shows a variant embodiment of the actuator;

FIG. 8 shows a variant embodiment of the actuator;

FIG. 9 is a block diagram of the electronic unit;

FIG. 10 shows a detail of the adaptation to the pedal;

FIG. 11 shows a variant detail of the pedal;

FIG. 12 shows a variant detail of the pedal;

FIG. 13 shows a practical embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the non-limitative example selected in order to illustrate theoperation of the invention, the power control member which is directlyunder the control of the driver is the accelerator pedal. The powercontrol is the throttle valve of an automobile. It could just as well bean injection pump or an electronic control device, in the same way asthe principle would apply also to any other motorized device. Referencewill first of all be had to FIG. 1.

The throttle valve (1) is pulled by a cable (2) actuated by the pedal(3) against the force of the spring (4). A mechanical connection (5)which is firmly connected with the movements of the pedal also serves todisplace the output member (6) of the actuator (7). As indicated in FIG.2, the mechanical connection (5) can also be entirely or partly commonto the actuator and the power control, in this case the throttle valve.

An electronic control unit (12) receives the speed measurement (8) froma sensor (9). Via the line (10) it also receives the set speed limitvalue established by the selector (16). This set speed can be selectedfrom among predetermined values, or it can result from the storing ofthe instantaneous speed. It may also be imposed by an externaldevice--remote guidance, safety marker, anti-collision system, etc.

The signal (11) formed by the electronic unit assures the control of theactuator (7) which is used as force control. When the speed of thevehicle exceeds the set speed, this signal controls the actuator in sucha manner that it produces on the pedal (3), by means of the outputmember (6) and via the connection (5), a controlled return force whichis opposite the force with which the driver acts.

The use of the actuator in force control is one of the essentialcharacteristics of this invention which distinguishes it from the priorlimiters or cruise controls in which the actuator is controlled inposition. Here, the point of application of the force may, on thecontrary, occupy any position whatsoever, since it is bound to thestroke of the pedal. Furthermore, the return force is controlled by theelectronic unit so as to be a function of the speed difference. Itsintensity and the progressive nature of its action are at all timesdetermined by the automatic control, independently of the displacementof the pedal. The actuator can adjust this force without interruption ofcontinuity from a value of zero to the maximum value of the operatingrange. It thus provides the driver with a quantified perception of thespeed difference. The return force is sufficiently great to displace thefoot of the driver, but it also brings about on his part a reflexreaction by which he instinctively maintains the vehicle at thepreselected speed. The proportionality which exists between the speeddifference and the force assures stable operation of the regulation.Despite everything, the driver can act with a greater force in orderintentionally to temporarily exceed the speed limit. This exceptionalposition is indicated by an alarm placed in operation when thedifference in speed is maintained at an excessive value. Furthermore,the return force is temporarily forced to a low value by the action of asignal controlled by the disengagement as well as when the speed ofdepression of the accelerator pedal, representative of intentionalacceleration, exceeds a predetermined threshold. The speed of the pedalcan be transmitted by a sensor integrated in the actuator or come fromoutside information. These solutions improve the comfort of driving andfully respect the freedom of action of the driver. Likewise, he can alsotravel at a lower speed, simply by letting up on the accelerator pedal;no maneuver is necessary for placing the system out of operation. Assoon as the speed of the vehicle is less than the speed set, theelectronic unit forms on the line (11) the signal which brings theactuator to a zero force. The apparatus is then no longer perceptible tothe driver.

It is worthy of note that the invention at no time limits the power ofthe vehicle and therefore its ability to accelerate, and that its usedoes not require any particular attention or action on the part of thedriver. Thus, the limiter cruise control is equally well adapted to citytraffic or busy highways, where it does not modify the driving habits,as to long trips on a highway at stabilized speed.

These characteristics distinguish the invention from the limitersdescribed in the prior patents, in which the control mechanism acts as amovable stop against the stroke of the pedal, even if such stop isresilient and can be exceeded by applying a greater force. In fact, theposition of the stop is adjusted as a function of the speed difference,and the hardness which it opposes to the pedal therefore depends on themovements of the pedal, both in intensity and in progressive character.The feeling of a hard point is therefore no longer reproducible and attimes sudden and without direct relationship to the speed difference.

The invention described here completely overcomes these disadvantagesdue to the fact that the intensity of the force and the progressivenature of its action are under all circumstances controlled by theautomatic control. The action of the device, which is soft, progressiveand in accord with the behavior of the vehicle, has the result that itsuse is never perceived as a restraint.

Another interesting feature is that, by construction, the force producedby the actuator is unidirectional. It can act only in the direction ofreturn towards zero speed and in no case in the direction ofacceleration, acceleration remaining strictly under the control of thedriver, contrary to the arrangement adopted on cruise controls. Thedevice is therefore intrinsically a positive safety device and does notrequire any additional artifice in order to overcome a malfunction.

The lines (13) and (14) can transmit safety signals to the electronicunit, for instance the "stop" alarm of automobiles and/or themeasurement of excessive engine speed, without these examples beinglimitative. These signals act by way of priority to adjust the restoringforce to the maximum, even when the limiter/cruise-control function isnot in operation, which improves the information to the driver andsafety.

The control of the traction slippage is effected in accordance with thesame principles: The electronic unit detects the slippage by comparingthe speed of rotation of the wheels and determines the correctionsignal. The different speed control, slippage, and safety signals arecompared in a maximum selector. The one which implies the greatestreturn force determines the signal by which the line (11) acts on thecontrol of the actuator, unless a disengagement action or anacceleration temporarily forces the control signal to a low value.

The electronic unit can also generate at least one electric outputsignal as a function of predefined criteria. As example, there may bementioned the absolute limitation of the maximum speed of a truck or anordinary transport vehicle by acting directly on the electronics of theinjection system. Similarly, the control of the slippage can act on theautomatic brake control or on the ignition of the vehicle simultaneouslywith the adjustment of the return force of the power control. Theseresults are obtained without additional investment.

FIG. 3 shows a simplified embodiment of the actuator which makes itpossible to understand its operation. It operates on the principle of anopen loop force control, obtained by displacing the components of theforces which a spring exerts on the lever of the output movement. Thiseffect is itself the result of the closed-loop control of the positionof one of the anchoring points of the spring. It is formed of anelectric motor (18) which is associated with a reduction gear (19) toform a geared motor of mechanically non-reversible movement. The outputshaft (27) of the geared motor drives in rotation a rod (28) the end ofwhich moves along the arc IJ. A copy system (23), a potentiometer orbinary coder,for example, is integral with the movement of the rod andtransmits to the electronic unit the information which permits theposition control of said unit. The position can also be determined bycounting the number of revolutions of the engine. The output member ofthe actuator which is in charge of transmitting the return force is thelever (6). It could also be a cable circular winding sector or any otherpivoting mechanical part capable of transmitting the force. This leverpivots at one end on a pin (17) which is aligned with the point I andintegral with the body of the actuator. It moves on a plane parallel tothat of the rod. The other end of the lever is connected to themechanical connection with the accelerator pedal; this connection can beeffected by a sheathed flexible cable. This end moves along the arc KLcorresponding to a proportional displacement of the pedal, K being theposition of rest and L the position of maximum power. A spring (20) isfastened to two pivots by which it is tensioned with a large initialtensile force between the rod on the one hand, pivot (22) and the leveron the other hand, pivot (21). When the pivot (22) is aligned with thepin (17), the tensile force of the spring does not exert any componentof rotation on the lever (6), whatever its position on the arc KL. Thereis therefore no return force on the pedal. In fact, a slightmisalignment of the pivot (22), directed towards J, makes it possible toassure the tensile force which is just necessary in order to maintainthe tension of the cable. Thus, the lever (6) accompanies the movementsof the pedal without the driver feeling the effects thereof. It is thisposition which the electronic unit imposes upon the rod as long as thespeed is less than or equal to the set speed. As soon as the speedbecomes greater, the motor is controlled in such a manner that the rodmoves from I towards J. The tensile force of the spring thereby producesa component of rotation on the lever (6). The position control of therod, and therefore of the pivot (22) on the arc IJ, which is a functionof the speed difference, also makes it possible to control the returnforce F which the driver feels. Zero in position I, the force is maximumin position J.

The force breakdown mechanism which is at the basis of the operation ofthe actuator can also advantageously be integrated in the acceleratorpedal, as indicated in FIG. 4. In this case, the lever (6) is replacedby an arm of the pedal or by an element integral with its displacement,directly subject to the traction of the spring (20). The rod (28), whichdisplaces the pivot (22) over the arc IJ, can be borne by the gearedmotor or articulated on an independent pin and driven by the gearedmotor by means of a mechanical coupling (FIG. 5) adapted to theconstraints as to force and space.

In the mechanisms of FIGS. 3 and 4, the displacement of the lever (6)over the arc KL slightly influences the return force, without this beingperceptible to the user. For other applications (robots, remotemanipulators, assisted controls, etc.), better precision in theregulating of the force and greater independence with respect to thedisplacement of the output movement can be obtained by various means:modification of the relative movement of the rod and the lever,replacement of the tension spring by a multi-turn spiral spring (26)actuated by a cable, as shown as a variant (FIG. 6), and particularly byadding a closed loop control, by means of a direct measurement of theforce. This measurement, transmitted to the electronic unit, can beeffected by a known sensor interspersed between the lever of the outputmovement and the use, or by strain gauges (30) integral with the body ofthe lever (FIG. 8). This two-fold, open-loop/closed-loop control permitsa precise and stable force control. For applications of this type, abi-directional control of the force can be obtained by positioning thepin (17) between the positions I and J of the stroke of the pivot (22).Without going beyond the scope of the invention. The actuator can bedeveloped in accordance with other variants which utilize the principleof control of the composition of the forces acting on the output member.FIG. 6 shows an embodiment in which the force is transmitted from therod to the lever by a cable which is guided by a pulley which turnsfreely on the pivot (22). The position of the pulley with respect to thepin (17) of the lever determines the amplitude of the return force. Thisarrangement permits greater flexibility in the selection of the spring.Among other things, it permits the use of a multi-turn spiral spring thevariation in hardness of which remains negligible with respect to theoutput movement. FIG. 7 diagrammatically shows another embodiment inwhich the pivot (22) is displaced in translation by a screw/nut system(25). For each of these embodiments, a variant construction consists inproviding a small single-acting damper (29) connected to the lever (6)on the one hand and to the mechanical base on the other hand, so as tolimit the speed of return of the lever and the impact of the pedal inthe event that it should be suddenly released. Whatever the variantembodiment adopted, the actuator has good dynamic behavior with respectto displacements of the output movement. Rapid movements of theaccelerator pedal do not produce any variation in force perceptible tothe user, which contributes to an agreeable feeling of greatflexibility. In fact, the return force depends only on the spring andnot on the reactions of an actuator. Furthermore, with constant force,the energy expenditure is zero. The average intensity required for theoperation therefore remains very moderate.

FIG. 9 diagrammatically shows the architecture of the electronic unit.It is developed around a single-chip microcontroller (49) interfaced inaccordance with the directions of the manufacturer. It integrates thefunctions of acquisition, storage, and action calculations and assuresthe position control of the rod of the actuator via a power interface(40). In accordance with a variant embodiment, the power interface canalso provide the position control function, in correspondence with theset value determined by the electronic unit and transmitted by the line(11). The speed measurement comes from a magnetic or optoelectronicsensor (9) which delivers a frequency proportional to the speed ofrotation of the wheels. For the limiting of the traction slippage, it isnecessary to provide one sensor per wheel. The set speed is selected bymeans of a small keyboard (16) read by the microcontroller. This may bea predefined value or the storage of the instantaneous speed. Theelectronic unit also reads on the lines (13) and (14) signals which areexternal to the system, safety set values or alarms, and controls byoutput lines (15) control devices of the vehicle. It also receives thesignal controlled by the disengagement, by means, for instance, of acontact, and the signal by which the program determines the speed ofdisplacement of the pedal. The different limiting and safety set pointsare stored in a memory which can rewritten and can be modified in situvery easily if necessary, among other things in order to keep in stepwith changes in the law, and they can also be locked. Briefly, themicrocontroller carries out the following program:

acquisition of input values;

calculation of the actions related to the values monitored and to theset values;

processing of the alarms;

selection of the largest of the actions;

processing of the disengagement and acceleration signals;

output of the control and signaling signals.

The calculation of the cruising speed is effected in accordance with thealgorithm known as proportional plus derivative action, with derivativeof the measurement. The adjustments of the actions are selected inaccordance with the rules of the art in order to obtain a control whichis adapted to the behavior of the vehicle. They are optimized at alltimes as a function of the speed.

The control signal of the actuator, line (11), is formed of rectangularpulses modulated in cyclic ratio. These pulses control the powerinterface (40) formed by an "H" bridge of field effect power transistorswhich deliver the energy necessary for the control of the engine. Theactuator sends, in return, towards the electronic unit the positioninformation which is read by the microcontroller in order to assure theposition control. The position sensor (23) may be of any known type. Asexample, there may be mentioned a potentiometer or a reflected binarycoder of low resolution, as well as generator of pulses controlled bythe rotation of the engine.

The microcontroller also manages the posting of the set value selectedand the maintenance procedure for modifying the adjustment parameters.

FIG. 13 shows a practical embodiment of the actuator. The geared motorcombines in a monobloc assembly an electric motor (18) and a worm speedreducer (19). It is fastened in a housing (32) the upper face of whichserves as mounting plate. The housing is provided with lugs to hold it,fixed in position, in the vehicle. The output shaft (27) of the speedreducer is equipped with a flexible coupling of the silent-bloc type(53), on the outer ring of which a collar is locked. This collarsupports the pivot (22) to which the spring (20) is hooked. The shaft(27) also drives the copy potentiometer (23) in rotation via a pinion(35). The lever (6) of the output movement pivots on the pin (17), whichis integral with the plate and the body of the actuator. It receives thetraction of the spring via the pivot (21). At the end of the lever, acoupling piece (36), which is free in rotation, locks the end of thereturn cable (5), which, in its turn, is guided by a flexible sheath.The displacements of the lever are limited by two stops (37) (38), andthe lever can act on the displacement sensor of the pedal, not shown inthe figure. Stroke ends, not visible in the drawing, and a safety stop(39) limit the stroke of the pivot (22) in case of failure of thecontrol. The power interface (40) is located in the housing. The entiremechanism is protected by a cover, the lever (6) of which extends outthrough a dust-shield joint.

FIG. 10 shows a possible embodiment of the return control for the pedalThe cable (5) coming from the actuator actuates an intermediate lever(41) freely mounted on the pin (42). One end of this lever, parallel tothe arm (43) of the pedal connected to the throttle valve, receives thecable head, while the other end exerts the force below the crank whichthe pedal forms. Pedal and lever are independent, so that the action ofthe lever can only raise the pedal again towards the position of zeropower of the engine. It can neither increase the power nor oppose thenatural rising of the pedal under the action of the return spring (45).

Any other means of mechanical connection which can act only in thedirection of traction is also suitable--flexible cable, articulated rod,etc. The embodiment (FIG. 4) which consists in integrating the actuatorin the pedal mechanism perfectly satisfies this condition.

FIGS. 11 and 12 show a variant embodiment in which the arm (44) whichtransmits the force to the foot of the driver is provided with aflexible connection of limited stroke, formed (FIG. 11) of anarticulation and a spring (47), or (FIG. 12) of a silent-bloc (48) or ofany other equivalent arrangement, such as a resilient pedal shoe. Thestiffness of the flexible connection is selected much greater than theresisting force of the springs (4) and (45) which pull back the pedal,although it does not flex in normal use. When the limiter enters intoaction with sufficient force, a fraction of the maximum force, theflexure of the flexible connection permits the displacement of the armof the pedal (44) even if the foot has not moved. This displacement islimited to a fraction of the maximum stroke by a stop (46). The force ofreaction which the actuator exerts on the foot of the driver is notreduced, but the action of the cruise control on the control of thepower of the engine is more efficient. This arrangement still leaves thedriver the possibility of overriding the limitation, at the price of aslightly increased pedal stroke.

What is claimed is:
 1. A power control assistance device for an enginehaving a power control member that is directly under operator control,said device comprising:a control unit providing a control signal inresponse to signals provided to said control unit; a speed sensorproviding a speed signal to said control unit; a set point selectorproviding a set point signal to said control unit; and an actuatormechanically connected to the power control member to provide a directcontrolled return force to the power control member, in a directionopposite to the direction of force exerted by the operator, in responseto said control signal.
 2. The assistance device according to claim 1wherein said actuator adjusts said return force from a minimum value toa maximum value without discontinuity, by displacement of the componentsof the forces exerted on the power control member by an output member(6) of the actuator (7).
 3. The assistance device of claim 1 wherein thepower control member is a pedal.
 4. The assistance device according toclaim 1 wherein said actuator comprises:a lever; a motor providingone-way movement of a given point in response to said control signal;and a spring connected between a point on said lever and said pointdisplaced by said motor so as to provide a force in response to saidcontrol signal that opposes a force that is applied to the power controlmember by the operator to increase the power supplied by the engine. 5.The assistance device of claim 4 wherein said lever is an arm of a pedaland the spring extends between said lever and a rod, said rod beingadapted to be driven by said motor.
 6. The assistance device of claim 5,said device further comprising:a pivot on said rod, said spring beingconnected to said pivot; a one-way damper connected to said lever toreduce said movement of said pivot; and stops adapted to limit thestroke of said lever.
 7. The assistance device of claim 6 wherein theposition of said pivot on said rod is a function of a force set valuedetermined by said control unit, and wherein movement of a pin on saidlever is limited, so that said lever is adapted to selectably provideforce in two directions.
 8. The assistance device of claim 1 wherein thecontrol unit provides said control signal to a motor through a powerinterface.
 9. The assistance device of claim 7 wherein said force setvalue is the larger of:a) the difference between the speed measurementand a speed set value determined according toproportional-plus-derivative-action, b) the difference between the speedmeasurement and a control signal determined by other information, c) thedifference between the speed measurement and a control signal determinedby the disengagement of the clutch which temporarily forces the forceset value to a low value when the speed of displacement of the powercontrol member exceeds a given threshold.
 10. The assistance device ofclaim 9 wherein said control unit is adapted to provide an alarmindication when said speed difference remains excessive.
 11. Theassistance device of claim 3 wherein said actuator is mechanicallyconnected to said pedal by a cable freely connected to said pedal so asto act only in the direction in which it is pulled, without interferingwith the natural return movement of the pedal.
 12. The assistance deviceof claim 3 wherein said actuator is mechanically connected to said pedalby way of an intermediate lever so as to act on the pedal only in thedirection of the reduction of engine power, without interfering with thenatural return movement of the pedal.
 13. The assistance device of claim1 wherein said actuator further comprises a flexible connection oflimited stroke between said actuator and the operator.
 14. Theassistance device of claim 1 wherein said flexible connection of limitedstroke is a resilient pedal surface.
 15. A power control assistancedevice having a power control member directly under operator control,said device comprising:an electronic unit providing a control signal inresponse to signals provided to it; a speed sensor providing a speedsignal to the electronic unit; a set point selector providing a setpoint signal to the electronic unit; and a servo-motor mechanicallylinked to the power control member, said servo-motor providing acontrolled direct return force in response to said control signal in adirection opposite to a force applied to the power control member by anoperator.
 16. The assistance device of claim 15 wherein said servo-motoradjusts said return from a minimum value to a maximum value withoutdiscontinuity.
 17. The assistance device of claim 15 wherein said powercontrol member is a pedal.